In measuring the conductivity of a liquid, such as a solution in a cell having two electrodes, conventional measuring systems apply to the electrodes an ac voltage in order to avoid polarization and related problems during the measurement. As the conductivity of the solution being measured changes, the resistance of the cell, and therefore the voltage drop associated with it, changes. A measure of this cell voltage drop is indicative of the conductivity of the solution. To obtain an indication of the conductivity, however, has in the past necessitated the conversion of the ac to dc before detection, or the use of an ac detection. These requirements have made the measurement of solution conductivity complicated, and the equipment for making such measurements expensive.
It is an object of this invention to provide a simple and inexpensive solution conductivity measuring circuit, preferrably one which can be packaged as a small unit; shaped like a pen, for example, for convenient carrying of the unit in ones shirt pocket. It is a further object of this invention to provide such measurements using a dc circuit arrangement utilizing integrated circuit packages in order to make possible the small size required for easy portability.